The present disclosure relates generally to material handling systems and methods. More specifically, the present disclosure relates to materials handling systems and methods involving a Bernoulli air flow.
Known systems and methods utilize the Bernoulli principle for providing a differential pressure to lift an object in a materials handling system. The differential pressure can be generated by transporting air through one or more passages to decrease pressure in a chamber. The decreased pressure in the chamber can lift the object.
In some systems and methods, the object is lifted and suspended in air while an arm or other positioning device moves the object. The object can be selectively lowered by decreasing the air flow in the passages, thereby decreasing the differential pressure. In some systems and methods, the object does not contact any portion of the system. In other systems and methods, the object does contact a portion of the system.
For example, the semiconductor industry utilizes many different wafer handling systems or wafer transport mechanisms. These wafers are thin, rigid objects that can be transferred through the use of tooling designed with the Bernoulli principles. Pressurized air or gas is forced through a small gap between two plates at an angle to each other and at an angle to the wafer. As the air escapes, it creates a low area of pressure just above the wafer which allows for lift. When the air is removed, the pressure equalizes which allows the wafers to drop or release from the tool. These devices include frictionless contact since the product does not contact the surface of the tool, but rather the rushing air acts as a frictionless bearing surface. Stability can be maintained in these by using small contact surfaces around the face of the tooling.
In the systems and methods in which the object contacts the system when it is lifted by the differential pressure, the object can adhere to the system. For example, the object can be forced into the chamber and remain in place due to friction from sides of the chamber contacting the object. This drawback is intensified with flexible objects. A flexible object can deform, wrap around, and/or compress within the chamber or other protrusions of the system when the differential pressure lifts the object to abut the system. When the flexible object adheres to the system, releasing of the flexible object may be delayed, slowed, and/or otherwise made inconsistent (i.e., the equalization of pressure can be interrupted).
What is needed is a system and method for lifting an object by applying a differential pressure, wherein the object can be controllably removed.